Components of cellular signal transduction pathways that regulate the growth and differentiation of normal cells can, when dysregulated, lead to the development of cellular proliferative disorders and cancer. Mutations in cellular signaling proteins may cause such proteins to become expressed or activated at inappropriate levels or at inappropriate times during the cell cycle, which in turn may lead to uncontrolled cellular growth or changes in cell-cell attachment properties.
Many proliferative disorders, such as tumors and cancers, have been shown to involve overexpression or upregulation of protein kinase activity.
Protein kinases are kinase enzymes that modify proteins by chemically adding phosphate groups (phosphorylation). Phosphorylation usually results in a functional change of the target protein by changing enzyme activity, cellular location, or association with other proteins. Protein kinases can be subdivided or characterised by the amino acids of the target protein whose phosphorylation they control: most kinases act on both serine and threonine, the tyrosine kinases act on tyrosine, and a number (dual-specificity kinases) act on all three. There are also protein kinases that phosphorylate other amino acids, including histidine kinases that phosphorylate histidine residues. The human genome contains about 500 protein kinase genes and up to 30% of all human proteins may be modified by protein kinases. Kinases are known to regulate the majority of cellular pathways, especially those involved in signal transduction. Dysregulation of protein kinases by mutation, gene rearrangement, gene amplification, and overexpression of both receptor and ligand has been implicated in the development and progression of human cancers. Protein kinase inhibiting compounds or protein kinase inhibitors (PKIs) are therefore useful for treating diseases caused by or exacerbated by overexpression or upregulation of protein kinases. For example, tyrosine kinase inhibitors (TKIs also known as tyrphostins) have been shown be effective anti-tumor agents and anti-leukemic agents (Lowery A et. al., Front Biosci. 2011 Jun. 1; 17:1996-2007).
A major objective of formulation chemistry is to improve drug efficiency and safety, by e.g. improving bioavailability and stability as well as convenience to the patient. Bioavailability means the rate and extent to which an active substance or therapeutic is absorbed from a pharmaceutical form and becomes available at the site of action. The most common and preferred method of delivery due to convenience, ease of ingestion, and high patient compliance to treatment is the oral route of drug delivery. However, for certain drugs, drug absorption from the gastrointestinal tract is limited by poor aqueous solubility and/or poor membrane permeability of the drug molecules.
PKIs are generally weak bases that dissolve only slightly at low pH (e.g. 100-1000 mg/L) and are practically insoluble at neutral pH (e.g. 0.1-10 mg/L). Therefore, enhancing the solubility and dissolution rate of PKI-based drugs is important for improving the bioavailabitity and efficacy of most of these drugs. Typical PKIs exhibit non-polypetide structure and have relatively low molecular weights, such as ≤10000 dalton or ≤5000 dalton.
Several methods to improve the dissolution characteristics of poorly water soluble drugs have been reported, including micronisation, formation of salts or solvates, complexes and microspheres. Additionally, attempts have been made to improve bioavailability provided by solid dosage forms by forming particles comprising the drug or by mixing the poorly water soluble drug with hydrophilic excipients. Traditionally, however, these methods carry inherent limitations concerning physical stabilities of the particles on storage, problems with grinding or difficulty of removal of the frequently toxic solvent. Furthermore, it is important that the drug released from the solid phase does not precitipitate in the gastrointestinal tract, or precipitates as little as possible, but remains water-soluble in the aqueous fluids of the gastrointestinal tract, since such precipitation results in low bioavailability (see e.g. Nerve J. et al. Pharm Dev Technol. 2011 June; 16(3):278-86).
pH-dependent solubility is a well-known issue for many oral formulations of poorly water-soluble substances, such as PKIs, since most of the absorption of the drug occurs in the small and large intestine, where pH is close to neutral. There is thus a continuing need to develop and improve the dissolution characteristics of oral solid dosage forms of PKI-based drugs. (Budha N R, Frymoyer A, Smelick G S, Jin J Y, Yago M R, Dresser M J, Holden S N, Benet L Z, Ware J A. Clin Pharmacol Ther. 2012 August; 92(2):203-13). Therefore, methods for improving dissolution of PKI-based drugs, as well as of other poorly water-soluble drugs, at neutral (intestinal) pH are highly desirable.
US20090203709 discloses a pharmaceutical dosage form comprising a solid dispersion product of at least one tyrosine kinase inhibitor, at least one pharmaceutically acceptable polymer and at least one pharmaceutically acceptable solubilizer. Further the reference discloses methods for preparing the above-mentioned pharmaceutical dosage form, comprising preparing the homogenous melt of at least one tyrosine kinase inhibitor, at least one pharmaceutically acceptable polymer and at least one pharmaceutically acceptable solubilizer, and allowing the melt to solidify to obtain a solid dispersion product.
EP2105130 discloses pharmaceutical formulations comprising a solid dispersion or solid solution, containing a polymer and an active agent in amorphous form. Further, the formulation comprises an external polymer to stabilize the solution, such that the % by weight of the external polymer is less than 20% of the total weight of the pharmaceutical formulation. Additionally, the reference discloses a hot melt extrusion method for production of the above-mentioned formulation.